Lubricant composition



LUBRICANT COMPOSITION Walter J. Coppock, Ridley Park,-Pa., assignor toSun Oil Company, Philadelphia, Pa., a corporation of New Jersey NoDrawing. Application September 1 ,0, 1943,

Serial No. 501,847

1 Claim. (Cl. 252-52) This invention relates to lubricants of improvedquality. More particularly, an object of the invention is to providelubricant compositions for general use which have a high degree ofstability with respect to oxidation. A further important object of theinvention is to provide lubricants for use in certain types of servicewherein the lubricant is required to be highly resistant towardoxidation and at the same time also is required to be efiective tosubstantially prevent rusting of the service equipment due to action ofwater.

It is well known that lubricating oils tend to deteriorate under serviceconditions, particularly through oxidation, forming undesirablesubstances such as acidic materials, resins, gums, sludge and the likewhich in one way or another result in depreciated performance. It alsois known to prepare lubricant compositions having less tendency towarddeterioration during service operation by utilizing in the compositionsrelatively small amounts of various organic substances which serve tominimize or inhibit oxidation. I have now discovered that thymol isparticularly effective in stabilizing mineral oil compositions againstoxidation and is well adapted to inhibiting or substantially retardingdeterioration of lubricants such as petroleum lubricating oils andgreases.

In accordance with the present invention lubricants of enhancedstability are prepared by incorporating thymol therein in amountsufiicient to impart the desired stability characteristics. This amountmay vary depending on the particular base oil employed but in any casewill be relatively small. Thus, amounts ranging from a small fraction ofone per cent up to three per cent, for example, may be used although,generally speaking, less than one per cent, for instance 0.1-0.5 percent is sumcient efiectively to inhibit oxidation. By adding thymol inthe aforesaid proportions, a wide variety of improved petroleum oillubricants, for example, lubricating oils for internal combustionengines, turbine oils, electrical oils, greases and the like, may beprepared.

In a special embodiment of particular utility the invention is directedto and provides lubricants which are resistant toward oxidation andwhich also are eifective to substantially prevent rusting of the serviceequipment in which the lubricants are used in the presence of water. An

outstanding example of a case in which the lubricant not only must havea high degree of stability toward oxidation but also must function asananti-rust agent occurs in the operation of steam turbines. Theserequirements cannot necessarily taining a good oxidation inhibitor mayvery sub- 2 be satisfied by the addition to the oil of a good oxidationinhibitor and a good rust-preventive. For example, various goodoxidation inhibitors are water-soluble to a. substantial degree andtherefore, in service equipment like that above specified, areinoperative. Again, the addition of a good rust-preventive to alubricating oil constantially impair the stabilizing power of the otherconstituent; for example, various amines (for instance ethyldiethanolamine) are good rust-preventives but destroy the inhibitingpower of oxidation inhibitors to such an extent that they are unsuitablefor use in lubricants which contain the inhibitor. In accordance withthe present invention both requirements are satisfactorily met byincorporating in the lubricant thymol to impart desired stabilitythereto and one or more compounds of a particular class of compoundswhich are excellent rust-preventives and which,'while slightly reducingthe efi'ectiveness of the thymol as an anti-oxidant, do not impair itsstabilizing power to a. materialdegree. I have discovered that thymolfunctions as an effective oxidation 5 inhibitor in the presence of waterand even when used in combination with these rust-preventive compounds;

The desired rust-preventive quality of the lu- .bricant is obtained byincorporating in the thymol-containing lubricant a relatively smallamount of a substance comprising a dihydroxybenzene which has attachedto the benzene ring one or more hydrocarbon groups having sufficientcarbon atoms to render said substance solube in oil and insoluble inwater. I believe that any substituted dihydroxy-benzene that iswaterinsoluble is effective to substantially prevent rusting. Theefficiency of substances of this class as a rust-preventive is due,presumably, to their capacity to cause the lubricant to wet, in th formof 'a-thin film, the metal surfaces and thus form a protective coatingthat prevents effective contact between the metal and water. I havediscovered that the detrimental eflfect of such substances upon theoxidation stability of a thymoi-containing oil is so slight as to beinconsequential in comparison with their great advantage as an anti-rustagent. However it is distinctly preferred to employ, as the anti-rustagent, those compounds of the broad class of compounds specified whichare derivatives of pyrocatechol (1,2-'benzenediol) having a hydrocarbongroup attached at the para position. This 1 preferred class ofcompounds, added to lubricating oil, is disclosed in the application ofW. An-

i-tertiary octyl-l, 2-benzenediol; 4-lauryl-1, 2-

benzenecliol; and 4-cyclohexyl-1, 2-benzenecliol. In these examples itis to be noted that the number of carbon atoms in the attachedhydrocarbon groups vary from four to twelve and that in all cases thesize of the hydrocarbon chains are such as to impart to the compoundsthe desired solubility characteristics. These compounds may be used inany eifective proportion, but it is generally satisfactory to employrelatively small amounts, for example, not over 2 per cent andpreferably 0.05-0.5 per cent. The stearyl derivative of pyrocatechol,which contains eighteen carbon atoms in the attached stearyl group,although having the desired solubility characteristics, is not aseffective as the above named agents and therefore must be used in agreater proportion in order to afford the desired protective action. Thelower eifectiveness of the stearyl derivative presumably may be due totoo large a number of carbon atoms in the attached hydrocarbon group;accordingly it is preferred to use derivatives having fewer carbon atomsin the attached group, for instance 4-12 carbon atoms.

The examples given below serve to illustrate the present invention butare not to be taken by way of limitation, since many modificationsobviously are within the scope of the invention. In these examples thelubricants concerned are of turbine oil type and accordingly have beenevaluated by a test method known as Rogers modified turbine oilstability test. In this method the lubricant in question is oxidized at95 C. in the presence of water and metal catalysts consisting of copperandiron and under rigidly controlled conditions until the neutralizationnumber of the oil has reached a value of 2.00 mgs. KOH per: gram, thetime required for reaching this value being taken arbitrarily as thelife period of the sample. The longer the life period, the greater isthe stability of the lubricant. This method is substantially thatdescribed in the article appearing in Industrial Engineering Chemistry,Analytical Edition, volume 13, pages 306- 312" (1941), entitledEvaluation and performance of turbine oils."

Example I Thymol in amount equal to 0.5 per cent by weight was added toa petroleum lubricating oi having the following specifications:

Gravity A. P. I 22.5 Flash point F.. 335 Fire point F 380 SayboltUniversal vis. at 100 F 155 N. P. A. color l 1% The resulting blend wassubjected to the Roger's modified turbine oil stability test, withresults as given below. For comparison, the original oil was tested inlike manner.

- Life period Oil without inhibitor hrs 50 Blend containing 0.5% thymolhrs 395 From the above data it is readily apparent that thymol is aneffective stabilizing agent.

Example I! A white oil having a S. U. viscosity of 150 at 100 F.,prepared by treatment. of a distillate fraction from a Gulf Coastalcrude with 200 pounds of fuming sulfuric acid per barrel in incrementsof 20 pounds per barrel, was subjected to the Roger's modified turbineoil stability test. Two blends of this oil, containing 0.25 per cent and0.50 per cent thymol respectively, also were sub- ,iected to the test,with results as follows:

Life period 150 vis. white oil hrs 85 Blend containing 0.25% thymol hrs1,570 Blend containing 0.50% thymol hrs 2,245

This tabulation clearly shows the effectiveness of thymol as anoxidation inhibitor.

Example 111 The original oil of Example I was used as base stock for thepreparation of a turbine oil lubricant having rust-preventive propertiesas well as a high degree of resistance toward oxidation. The turbine oillubricant was prepared by blending the base stock with 0.2 per cent4-tertiary butyl- 1,2-benzenediol and 0.5 per cent thymol.

The blend was tested according to A. S. T. M. tentative method D665-42Tfor evaluating rustpreventing characteristics of turbine oil, describedon pages 274-276 of the publication entitled, A. S. T. M. Standards onPetroleum Products and Lubricants. issued October 1942. In this test ahighly polished steel specimen is maintained in contact with oilcontaining 10 per cent water at a temperature of 140 F. under carefullycontrolled conditions for a period of 48 hours. In order that the oilpass the test the steel specimen after this period oftime must be freefrom rust. The blend passed the test, the entire surface of the steelspecimen being free from rust. Subjection of the same base stock,without the addition agents, to the same test resulted in failure, with80 per cent of the steel specimen exhibiting rust. 4

The oxidation stability of the blend was determined by means of theRogers modified turbine oil stability test and the life period of theblend was found to be 333 hours, as compared to 50 hours for theunblended stock and 395 hours for the stock blended with 0.5 per centthymol but with no anti-rust agent (see Example I). This demonstratesthat the stabilizing quality of the thymol was not seriously adverselyaffected by the addition of the anti-rust agent. By way of contrast, ablend of the same base stock with 0.1 per cent ethyl diethanolamine and0.5 per cent thymol, although having satisfactory rust-preventivequalities by virtue of the presence of the ethyl diethanolamine, had alife period of only 58 hours; thus showing that this particular antirustagent, in contrast to the anti-rust agents of the present invention,substantially destroyed the stabilizing quality of the thymol.

In the appended claims whenever reference is made to a. substituteddihydroxy-oenzene, it should be understood that this refers to acompound resulting from replacement of nuclear hydrogen in adihydroxy-benzene by at least one hydrocarbon group.

What I claim and desire to protect by Letters Patent is: I

A mineral oil lubricant composition containing a small proportion ofthymol effective to substantially inhibit oxidation and a smallrust-preventive proportion of a substance comprising a substituted1,2-dihydroxy-benzene having as the substituent a saturated aliphatichydrocarbon group attached to the benzene ring in the para position andcontaining 4-12 carbon atoms.

WALTER J. COPPOCK.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Number Name Date Rather Mar. 13, 1934 CloudMar. 3, 1942 Prutton Oct. 13, 1942 Reiff Aug. 10, 1943 Musher Jan. 25,1944 Loane Mar. 19, 1940 Van Ess July 4, 1944 Weissberger Nov, 13, 1945FOREIGN PATENTS Country Date Great Britain Apr. 14, 1938 France Oct. 22,1937 OTHER REFERENCES Rancidity in Edible Fats, by Lea. (1938), p. 172.

Uses and Applications oi Chemicals and Related 9

